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How does a small aircraft like a Cessna fly at night?
What happens when a small aircraft like Cessna is flying in daytime then night hits and its now pitch black with zero visibility? How does he not run into mountains and the like?

A good map helps. Pitch black does not mean zero visibility and a good pilot knows the minimum altitude in the area to avoid terrain. If it is zero visibility, you need an IFR rating and flight plan, otherwise you have typically less than 3 minutes to live after entering IMC (instrument meteorological conditions).

Ok so basically a map and know the minimum altitude along with IFR or basically if you don't know exactly where you are or where your supposed to be your dead

Most places you have plenty (too damn many, IMHO) of ground lights for reference.  Even in places where those are few or nonexistent, you usually have the moon and stars.  FWIW, the only place I can recall seeing no lights at all is between Gabbs and Walker Lake in Nevada, and that was a couple of decades ago.

Unless you want to emphasize a difference between GA aircraft and larger ones, this question is related and maybe a duplicate: How can pilots fly inside a cloud?

Cessna 170 = small & Boeing 737 = big

Lets attack this from a few different angles.

then night hits and its now pitch black with zero visibility?

There is plenty of visibility at night, a clear night is just as nice as a clear day. As a matter of fact when the air cools at night and clouds roll out you can some times see farther than you can during the day.
Here's me on a VFR approach (Piper Warrior) in to KLNS at about 10pm one night, you can see the runways are lit up nicely and can usually be spotted from 5 - 10 miles out depending on altitude.

Here is us earlier that night heading away from KABE (those lights are Allentown PA)

(photo credit to my girlfriend who was bravely sitting in the back)
As you can see you can still make out the horizon and plently of land marks. While it may be different during the day you can still fly VFR at night.

zero visibility?

Zero visibility during the day is the same as zero visibility at night and as mentioned in the comments will require you to fly IFR if you want to fly.,

How does he not run into mountains and the like?

Not flying into the side of a mountain is a topic of its own. You should check out my answer here to that very question.
From a more general stand point there are lots of ways to navigate in an aircraft. Here is a solid answer that covers most of them. The only thing that is not really feasible in a small single pilot aircraft if you are solo is celestial navigation although it could be done.

Without an IFR rating large bodies of water can be a bit of a challenge. JFK Jr found that out the hard way

First, let's get the obvious answer out of the way: the aircraft flies fine, it doesn't know it's night. It's the pilot who may have issues with night flying.
It's true that night flying isn't the same as day flying, and some countries require additional training or even an instrument rating for night flight, but in the US (for example) night VFR flight is allowed and night training is included in basic pilot training. VFR at night is still visual flying, and if you can't see where you're going then you need to stay on the ground. Unless perhaps you have an instrument rating, but operating in night IMC in a single-engine, single-pilot aircraft is considered fairly risky by many pilots, especially if it's over rough terrain.
To address a couple of your specific points:

Night doesn't "hit"; sunset is a well-known and easily planned for event. A pilot's flight planning should never be so poor that night comes as a surprise.
Night is not "zero visibility". With a full moon and clear skies, you can see a very long way. And unless you're in a remote area, there are usually plenty of lights visible on the ground. On the other hand, it's certainly true that some nights are darker than others, and if you fly into a cloud at night then you will indeed lose all visibility immediately. That's why most countries require some form of instrument training for night flying, even if it's very basic.
While pilots do occasionally run into mountains, it's also something that they plan to avoid by choosing a good route and altitude. This is also where night training helps, because you learn things like paying attention to lights (including stars) that suddenly disappear: that means something is now between you and the lights, and you need to have a reasonable idea of what it is. A GPS with terrain features can be very useful.

Of course there are some specific challenges to flying at night, and they're addressed in training. There are sensory illusions that only occur at night (or in very poor visibility), like black holes and autokinesis. There's also a tendency to fixate on the largest, most visible light sources and fly towards them even if it takes you off course. And judging height, distance and runway length are all a little different too, which is why pilots who haven't flown at night for some time should always go up with an instructor first, to refresh their memory.

do small aircrafts have GPWS ?

@v.oddou not typically, no. Newer avionics packages have "synthetic vision" systems which is a computerized representation of the surrounding terrain, or even night vision, neither of which can be used for primary vision in VFR flight.

@v.oddou Some do, terrain maps and warnings are included in the Garmin G1000 and similar, newer panels. And many light aircraft pilots use tablets with flight tools like ForeFlight or Garmin Pilot which can also provide terrain warnings, including audible warnings if you link it to a Bluetooth headset. But not everyone has (or wants) those things and it's certainly not standard equipment.

First of all, a day does not transition into a pitch-black night instantly, but gradually. When an airplane is on an altitude of 2000-3000 feet, most of the building structures and hills etc. are not an obstacle anymore and the pilot has a much better visibility.
For flights initiating during daylight and going to night time, there are several things which are considered.

Planning
A pilot, most of the time, plans a flight thoroughly. It includes the final destination, duration to that destination, the route, terrain underneath, weather conditions at present and the changes expected, expected traffic and many other things.
Pilot
For pitch black darkness, pilots are specially trained and are instrument flight rated.
Aircraft
The aircraft have specialized and enhanced equipment which helps the pilot to navigate during such a time. Most of the time, an IFR pilot flying an airplane for night flying has enough help through different instruments in the plane that he does not need to visually be looking outside. Hence the terms IFR vs VFR.
Other things
Many other things are considered. You can read those on AOPA or PlaneAndPilotMag.

It may be a little misleading, it reads like night flying requires an instrument rating. As odd as it sounds, VFR pilots can legally fly in the dead of night with very little visual cues without instrument training (other than that required during PPL, which is almost nothing).

@RonBeyer Your comment is correct for the US, but some other countries require night ratings or even instrument ratings for night flight (i.e. night VFR isn't allowed).

@Pondlife True, either way it should be clarified.


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What does a drone do when it's out of control range?
According to regulations, what should a mini-drone do once it is out of the control range?  Would it continue flying even if it receives no signal?
What about full size drones?

It would do whatever it was programmed to do, which is a question only the manufacturer can answer.

It's clear from a quick glance at the manual that this is only a toy, so I don't think the question is relevant to the aviation community.

@DanHulme I understand it's only a cheap toy, but where else do drone questions go to? Also a cheap toy it might be, the fundamental physics behind it is no different to a helicopter.

This site is not "for all questions that don't have anywhere else to go to". I think that comparing it to a helicopter is a bit unreasonable when your question is specifically about the remote-control aspect. For general advice on the issue, see this related question.

There is a unmanned-aerial-vehicle tag, yep, mainly for drones.

@Telkitty: Are you aware of the existence of the websites diydrones.com and rcgroups.com? Both are home to very large communities of hobbyist pilots (70 thousand for diydrones and millions for rcgroups). There are other smaller sites out there like flitetest and fpvlab but almost everyone flying any sort of unmanned aircraft gravitate towards rcgroups sooner or later

@Telkitty: I'd also like to note the importance of rcgroups.com to the hobbyist community (and even the larger aviation community). A lot of the drone software you find out there can be traced back directly to discussions on rcgroups - yes, people develop software while talking to their friends on rcgroups. A lot of the software like KK2 and MultiWii are basically community projects born out of forum discussions. There are even real-life UAV developers who hang out there (though they usually can't say much about their past projects - they give good advice though)

Anyways, what is a "full size" drone? Military? https://en.wikipedia.org/wiki/Controlled_Impact_Demonstration?

@SMSvonderTann - agreed. It might be helpful to define the different between "mini" and "full size" to help get better answers.

Let's take it from the top: it depends on the drone
Regular, off the shelf hobby drones, might just turn off and then fall to their doom. Some more expensive ones, might have a feature to safely land (instead of dropping like a rock).
Considering military ones, it all depends on the programming and the manufacturer. Some drones have parachutes, so that could aid them when they run out of juice.

This is true, although others will have a "reverse course" type of functionality to either track back the way they came, or fly towards where they launched, or will just stabilise and hover until you can get back into range.

Depending on your drone, the drone will probably stop moving and land safely. Or it will continue flying until there is no power left. There are no regulations about this and this question can only be answered if you try it out yourself or ask this to your manufacturer.

Or return to take-off point or specified landing coordinates. Depends entirely on the drone whether you can set these.

@RoryAlsop Agree, DJI has it's fail safe mode if it is out of range and will return back to the HOME position until the drone is within range again. But the Syma X5C just continues to fly until there is no battery power left.

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Why does not the lift produced by main wings create pitch moment?
Pitch moment is created by lift created by the horizontal stabilizers via the elevators.
But then main wings also create lift, why does not this lift enough to create pitch moment?

The wings of most aircraft are located at or near the centre of gravity. Aircraft like the Concorde do have the pitch moment created my the main wing because it also acts as the horizontal stabilizer.

Lift moment is a force (the lift) and a lever (the distance between the aerodynamic center  and the CG). As long as they are not null, they induce a pitch change. Fortunately the lift moment of the horizontal stabilizer and the elevators cancels it. See Pitching moment.

Of course it creates a pitching moment! Now we need to define around which reference point this moment should be measured.
If the reference point is the center of gravity, it is even equally strong as the pitching moment of the elevator, it only has the opposite direction.
If you use the aerodynamic center as the reference point, the moment will be less strong. If the wing airfoil is symmetric, the moment will actually be zero (ideally), but with a cambered airfoil there is still a measurable moment left.
A moment is always a combination of a force and a lever arm, measured perpendicular to the direction of the force. Only when the lever arm is zero will the moment disappear. If we use the center of gravity as the reference point, the weight will have no lever arm and will contribute no moment, but the distance between the wing's lift and the center of gravity is large, so this moment is large, too.

Would it be correct to interchange orthogonally and perpendicularity?

@Terry: Yes, I guess. Which would be more natural for you native speakers?

My guess is that American English speakers not technically educated would often hesitate upon encountering orthogonally. I probably would have said "measured perpendicularly" or "measured perpendicular", but I'm not sure if both of those are grammatically correct.

Native English speakers conversant in higher mathematics would understand "orthogonal", but might think it an odd choice of words; "perpendicular" is the far more common term. "Orthogonal" is often used by mathematicians to denote a relationship more general than mere perpendicularity, like orthogonality of basis vectors in a vector space. Computer scientists on the other hand think of orthogonality as the ability to alter parts of a system without worrying that the change will impact other parts, and that is certainly not the sense meant. "Perpendicular" is the right word choice here.

@PeterKämpf Why do they cancel it? CG is ahead of wings toward cockpit. Now lifts produced by both main wings and elevator are behind CG which should mean they both are creating the moment in same direction. Then why do you say they are in opposite direction? May be I am wrong somewhere, please correct me.

@PeterKämpf see this image. CG is ahead of wings. https://www.google.co.in/search?q=center+of+gravity+location+aircraft&espv=2&biw=1280&bih=619&tbm=isch&imgil=9ly2ZBny2CSA7M%253A%253BTeMAwXqTpeiTWM%253Bhttps%25253A%25252F%25252Fwww.grc.nasa.gov%25252Fwww%25252Fk-12%25252Fairplane%25252Facg.html&source=iu&pf=m&fir=9ly2ZBny2CSA7M%253A%252CTeMAwXqTpeiTWM%252C_&usg=__DVYg-J7uNpGM5AQT_37691ZbxKQ%3D&dpr=1.5&ved=0ahUKEwij64q1mvrKAhXGCY4KHX4aDn0QyjcILw&ei=F__BVuODGMaTuAT-tLjoBw#imgrc=9ly2ZBny2CSA7M%3A

@user2409011: Even though the label on the picture says NASA, the cg location is too far forward. Use the main gear as a guide: A line up from the wheel slanted 15° forward from the vertical will cut through the cg at maybe 30%-40% of fuselage height. Also, the tail surface produces little lift and sometimes even a small downforce in cruise. Look at the camber of the horizontal tail: It is opposite to that of the wing.

Pitching moment is usually defined relative to the centre of gravity. The main wing does provide a pitching moment, since it has both a force and a moment arm relative to CG.
The reason to define pitch relative to CoG is that in a free response in vacuum, the CoG is the centre of pitch rotation. But moments can be defined relative to any point, also to the centre of lift of the main wing, which holds the aeroplane up when flying. And if we do that, we can see why the tailplane lift often points down, not up:

Total pitching moment must be zero in steady flight.
In the depicted situation, if the tailplane stalls, its lift and pitching moment contribution is cancelled - the n.p.$_{fixed}$ moves forward to the a.c.$_w$. There is now a nose-up pitching moment, tending to want to stall the aeroplane.
Therefore, relative to the a.c.$_w$, the fail-safe situation is a gravitational moment nose-down and an aerodynamic moment nose-up: c.g. in front of a.c.$_w$, tailplane lift pointing down.

As mentioned in this answer this is mainly a safe configuration at low airspeeds. At higher speeds the upwards lift of the tailplane is fine and will create an aerodynamically stable configuration.

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What cargo airplanes can transport fully assembled large turbofan engines?
Is there a big demand for transporting overseas for turbofan engines with nacelles like TrentXWB or GEnx by cargo airplanes ? If yes, what planes are used?

Somewhat covered here: Can the A380 ferry an extra engine, like the 747?

http://www.rolls-royce.com/products-and-services/civil-aerospace/products/civil-large-engines/videos/trent-900-on-board.aspx

Engine nacelles are part of the aircraft and not the engine. I think you're asking about fully assembled engines.
Oversized jet engines are usually transported by road when possible; in case air transport is required, the Antonov An-124 'Ruslan' is your best bet. It is the only aircraft capable of transporting engines like the Engine Alliance GP7000 and RR Trent XWB.

Image from antonov.com
For smaller engines (or partially disassembled ones), other aircraft like the Boeing 747F and A330-200F are used.
Interestingly, this filing with US DoT shows the An-124 being used to transport GE GEnx engines from Rickenbacker airport to Seattle to ensure smooth production in Boeing factories.

I am person who asked this question. I know that an124 transport fully assembled GEnx, but this was emergency need. I am interested on how regular volumes are transported overseas such as Trent1000 from UK to Seattle. It could be by B747F if outer nacelle separately from core, but this is my assumption. I also presume that GE90 are transported by truck from Ohio to Seattle, as well as Trents to Toulouse, its not overseas as well. Am I correct. But if it is necessary to deliver Trent from UK to Singapore of GE from Ohio to Hamburg - how it is done ? By an124? But it is expensive! Who knows?

Notice this picture shows the engine already mounted on the vehicle needed to mount the engine.

I can't really answer this, but generally, there's no reason to transport fully assembled engines. They'd have to be taken apart into order to be installed anyway. The props would overbalance and overload the assembly used to raise and position the engine to properly bolt it in place. The cowling would have to be removed to allow access to connecting lines to the aircraft. Ditto the prop. Besides, in most engine changes, there's no reason to replace the cowling.I once flew on a C-130 that was carrying a R-28 engine for a C-124. It wasn't even a strain.

Prop engine would be transport without the prop but what about turbo fan engine? They can be transported as a single unit and installed as such.

Yeah, that would be more difficult. And Less difficult. A propellor is kind of clunky to carry. A turbofan with fit nicely in some cargo craft (C-130s to C-17s, yet a complete engine is still unneccesary. External cowling, for one thing. If the cowling's damaged, the plane's probably's beyond flying and will need some support personnel and tools. Any ancillary equipment that's also necessary to the engine will not be brought along. I've flown in a C-141 carrying a complete (though partially disassembled) huey and a 4  door Chevy. It's amazing what you can pack in on of those things.


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What would be the lift formula for straight wings?
I have been trying to estimate the lift calculation for a straight wing. The previous project I worked on was a swept wing. But this is a straight wing. I would like to to get the stall speed so I need the Clmax formula. What would the lift formula for this type of wing be?

Change the cos$\varphi$ terms to 1 and the sin$\varphi$ terms to 0. Then the method for swept wings works for a straight one.

Regardless of the geometrical shape of the wing, you need to know the wing area to determine the lift force as it is one of the factors that affect lift.
Calculate lift using this formula: $$Lift = \frac{1}{2} (C_L * P * S * V^2)$$.

$C_L$: coefficient of lift
$P$: density of air
$S$: surface area of the wing
$V$: velocity of air

Yo have the lift given by :
$$ Lift = \frac{1}{2}\rho S V^2CL $$
The linear part of the lift curve can be approximated by formulae coming from the lifting-line theory :
$$CL = \frac{dCL}{dAoA}\left(AoA-AoA_0\right)$$
With the lift slope given by :
$$\frac{dCL}{dAoA} =\frac{2\pi}{\sqrt{1-M^2+\left(\frac{2}{AR}\right)^2}+\frac{2}{AR}} $$
Still you cannot compute the $CL_{max}$ from this and this stands for a straight low aspect ratio wing in the subsonic domain.
If the overall span of your wing is $2b$ and the chord is $c$ you have :

The wing surface : $$S=2bc$$
Its aspect ratio : $$AR = \frac{(2b)^2}{S}=\frac{4c}{b}$$

For the zero-lift angle of attack ($AoA_0$) it's approximately the one of the 2D-wing section if the wing is untwisted and if the wing section has a constant shape.


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How can the Antonov AN 225 only have 2 nose wheels?
I was watching the video of the AN 225 unloading at Perth airport this weekend, and it suddenly occurred to me that there are about a zillion rear wheels on the aircraft, yet only 2 nose wheels?
This might make sense in a normal airliner, but in this one, the whole weight of the 117 Tonne generator is passed over the front wheels, as it is unloading?

note from the first photo that there are 2 nose struts, with 2 wheels each, and from the last photo you see an external ramp supporting some of the weight. Interesting question nevertheless.

Yes I suddenly thought of the support on the ramp. But nevertheless, would still take the weight on landing and taxiing?

Nose wheels are designed to take only a minor part of the weight on ground. The balance required for flight constrains the CoG to be near the main gear also on ground.

OK so I'm guessing the cargo would have been secured directly over the wheels in that case?

Note that maximum take-off weight is 640 t. The main gear needs to support that. The 117 t cargo is quite light compared to that and the nose gear only needs to support it for short while during loading or unloading.

How can the XB-36 only have single wheel main gears?

The reason An 225 has only two nose landing gears (for a total of four wheels) is that it was developed from An 124 Ruslan, which had pretty much the same arrangement. This works during normal operations as the MLG take up most of the load.
However, for loading/unloading, the wheels are not loaded- the nose landing gear is folded, while a support strut comes out, which provides the necessary support and load carrying capacity, as shown below (thanks to @Federico for finding the image).

Image from airliners.net
In this image, you can clearly see that the NLG is folded and the weight is supported by the struts.

Image from news.yahoo.com

@Federico The last image shows the mechanism in quite some detail. Good find :)

@Federico Added it. Thanks :)

I assume that the close up of the NLG/support strut is from the right side of the plane, looking forward?

@FreeMan I think its the other way around- from the port side looking into the cargo hold; you can compare with the folded landing gear in the second image.

Ah, yes, thank you @aeroalias, I see it now. The green structure is part of the ramp folded up. I kept picturing that as the gear bay with some very large doors (which I realize now I magically couldn't see anywhere).

The An225 was designed to "kneel" to make it easier to load. Without this ability, specialised loading equipment would be needed at the airport to service it. It has nothing to do with the landing gear configuration. In their upright configuration, the forward landing gear will be more than capable of taking the weight of whatever is being loaded, however they cannot do so when folded - hence the pads for the aircraft to "kneel" on. Take the nose loaded 747 as an example, which has a similar nosegear configuration, and doesnt require any additional supports.

@GavinCoates It has nothing to do with the landing gear configuration and this answer does not claim anything contrary to this.

When an aircraft lands, the nose wheel remains elevated, and the main wheels touch down first. This results in a considerable impact on the runway as all of the weight of the aircraft hits the ground. In order to minimise the impact, and prevent damage to the runway, larger aircraft tend to have multiple bogeys on the main wheels to distribute the weight over a larger surface area.
Due to the sheer size, and unique mission of the An-225, it features a number of wheels in order to maximise the weight distribution on the runway surface, allowing it to carry a greater weight, and operate from smaller airports with weaker runways.
The nosewheel does not suffer from this problem, as the landing impact is much softer due to the main wheels taking most of the weight.
Interesting aside: The A320 can be purchased in both a single-pair and dual-pair main wheel configuration. So far, Indian Airlines (now part of Air India) are the only airline to operate the dual-pair main-wheeled A320, as the standard of runways is not as good in India, and therefore they can serve airports they otherwise wouldnt be able to do.

I've got to say, I haven't been able to find any reference to a single-nose-wheel A320 configuration, and your picture looks like it could be 1 or 2 wheeled. Do you have a better picture to show a single-wheel nose gear A320? We even have an answer here at Aviation.SE showing the A32x family all have 2-wheeled nose gear.

@FreeMan - I was referring to the main gear.

To clarify - I was referring to single-pair, and dual pair, main gear. I've edited to clarify that.

Even Air India ordered later models of the A320 with single-pair main gears.

I don't think this really answers the question, but interesting fact about the A320. There is a lot of difference in the design of single and multi boggies, so I am pretty impressed that is an option.

authors: Постер Каину


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What is this smoke coming from an airplane wing when it is landing?
I noticed that when an airplane is landing, the end of the wing emits a smoke like the one here: .
What is that?

It's a vapor trail. See also http://aviation.stackexchange.com/questions/14539/what-causes-a-planes-wing-tips-to-leave-a-small-white-vapor-trail?s=2|1.0543

Yep, it's the wing tip vortex.


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What is the significance of the V1 ground roll of an aircraft?
What is the significance of a V1 ground roll of an aircraft trying to take off? Why is minimum ground roll is measured in feet? What is the significance of VR (which is greater than V1 but less than V2)?

I'm not sure exactly what you are asking about in relation to the V1 "ground roll", but this question/answer discusses V1 in depth: http://aviation.stackexchange.com/q/3564/69

The post that Lnafziger tells the V speeds pretty well, V1 is the "point of no return" at which the pilot is committed to taking off. Vr is where the pilot needs to rotate the nose of the aircraft up so that you can fly, and V2 is when you are flying. V1 "distance" lets the pilot know how far down the runway they can be and still abort. Its measured in feet because runway distances are published in feet.


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How does an elevator offload function works in fly by wire flight control systems?
In some fly by wire systems I found that there is no trim in the traditional sense. I believe it is because the forces that pilot feels on the stick are artificial. I was told that those fly by wire systems has elevator offload functionality that moves H-stab.

Can anyone explain how elevator offload functionality is implemented?
Does the artificial feel system generate force in response to airspeed and vertical acceleration? (like making pilot push harder for every knot/every G away from the trimmed state?)
Is trimming necessary for FBW systems and if so How does the fly by wire system implements the trim?

From Lufthansa Technical Training Manual for 777

Elevator Offload Function
Operates only in the AirCommands to Determine when the Elevator is not at the Neutal Position for more tahn two seconds minimum.Commands the Horizontal Stabilizer to move as a Function of Airspeed. The Movement of the Horizontal Stabili-zer then causes the Elevator to move to the Neutral Position

Seems like an answer to me, @GHB!

Hi @FreeMan, I am quite new, I tend to agree but is a partial one though! What should be done in these cases?

@GHB - make it an answer. If others feel it's good, they'll up-vote you. if they feel it needs work, usually you'll get some comments on how to improve it. Occasionally, you'll get a drive-by down-vote with no idea why...

@FreeMan Thanks!

Regarding the first point, from Lufthansa Technical Training Manual for 777, page 30:

Elevator Offload Function
  Operates only in the AirCommands to Determine when the Elevator is not at the Neutral Position for more than two seconds minimum.Commands the Horizontal Stabilizer to move as a Function of Airspeed. The Movement of the Horizontal Stabilizer then causes the Elevator to move to the Neutral Position

That's a long document, if you can indicate the page number, that would be helpful.

@FreeMan Thanks, done!


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What drives and/or allows the move to higher-bypass turbofans on jetliners?
Note: I'm by no means an expert on any of this, I'm just curious.
There seems to be a general trend toward higher and higher bypass ratios in commercial jetliner engines. (I'm thinking here of 737/A320-size and larger aircraft.)
I understand why this is happening (fuel-efficiency & noise). But what has dictated the odd pace of the development?
There was obviously a drive toward higher bypass early on. E.g. P&W JT8D engines introduced in 1962 ran at 0.96:1, while - just a few years later in 1966 - the JT9D ran at 5:1. Quite a leap.
But then it seems to me that it settled around 5-6:1 for 25 years. Next big leap seems to be the GE90 in which runs at 9:1. That was 1992 and then it largely settled again at 9-10:1 for another couple of decades. The latest (smaller) leap appears to be the PW1000G at 12:1.
What has caused such sudden jumps and plateaus? Why hasn't there either been a more linear progression from the 1960s to now? Or a much faster progression toward the ratios we see today? They're obviously desirable.
I can just imagine P&W engineers looking at the JT9D in the mid-1960s, and thinking "well, we went from 1:1 to 5:1 in one go. Let's go for 10:1 next!". But that didn't happen. It seems their next major airliner engine was the PW2000 - fully 20 years later - at 6:1.

Was it due to technical/manufacturing limitations?
Has the emphasis on certain performance characteristics shifted? E.g. settling more permanently on economy over speed.
Is it simply that fleets stabilized around certain aircraft, and no new engines were needed/wanted for a long time?

The last point seems very plausible. Even so, the 747-8, 737-MAX and A320neo, while being comparable to their ancestors in size and role, have made sudden jumps from 5-6:1 to 10-12:1 engines. That feels like something that could conceivably have happened earlier or more gradually.
Of course I know that bypass ratio isn't the only interesting metric for an engine, but it's a noticeable one, even to the untrained eye; engines are simply becoming bigger and bigger. But that's also why I'm asking about the pace of development, since "making the fan bigger" seems like an obvious step to take (I know there's more to it but still). It also seems like something that'd be more likely to happen gradually, rather than in spurts.
Again, I'm no expert, I've just been googling. But I may have missed something basic.

your statement about the P&W JT8D leaves me in doubt about my understanding of bypass ratio. How can it be <1:1 ?

And I also wonder why '@Flambino' keeps disappearing at the beginning of my comment... Must be a quirk of the iPad app I work with.

@RobVermeulen How can it be <1:1? If more air goes through the core than around it. E.g. with a 5:1 engine, five times as much air goes around (bypasses) the core, as goes through it. With a 0.2:1 engine, it'd be the opposite: Five times as much air through, as what goes around.   And: It's not your iPad. Since you're commenting on my question, the @flambino part is implied: I'll see your comment automatically. You only need the @ if your comment is directed at someone other than the post's owner.

Thanks Flambino, for making me wiser on two topics at once! I failed to realize there is always air bypassing the core obviously, and that it is part of the ratio calculation.

For a clue look at the development in the price of oil:

Historical oil price chart (source)
While the first development into the 5:1 region predates the first oil crisis (1973) and was driven by fuel economy, better range and lower airport noise, the next step was kicked off by the second crisis in the early 1980s. It took one decade to develop the engines and the airplanes which could fit them, so the Boeing 777 - GE90 combination came out in 1995 in a time of falling oil prices.
The next round was only kicked off after the US invasion of Iraq which made oil prices shoot up from 2003 on. Again it took a decade for the engines to become available, but now the increase in diameter is less dramatic and existing designs can be fitted with them (A320neo, 737MAX).
Before the early 1960s the bypass ratio could not grow more because

jet engines were developed for military aircraft, and more emphasis was placed on top speed than on efficiency. Airliners used what was available (note that the Convair 880 was powered by a simplified, non-afterburning version of the J-79, which powered the F-104 Starfighter, the F-4 Phantom II and the B-58 Hustler).
early airliners (De Havilland Comet, Tupolev 104) had their engines in the wing roots, so little space was available for an increased bypass ratio. When Rolls-Royce was developing the first turbofan engine, the Conway, they limited the bypass ratio to 0.25 so it could fit into the Comet and the HP Victor bomber, which also had its engines in the wing roots.

The first oil crisis of 1973 kicked off the development of the unducted propfan (UDF) engine, which has been held back by noise problems. Again, it took about a decade until it could take to the air.

GE36 UDF engine fitted to the MD-81 (picture source)
The development of a new engine takes longer than that of an aircraft, so every time a big push, triggered by a substantial jump in oil prices, was needed to start the development of a new generation with significantly higher bypass ratio. Once the engine technology was ready and certified, it would be quickly incorporated into many models, because the better fuel economy would force everyone to upgrade.

Naturally oil price is a root cause, but I had not taken development time into account. Certainly makes sense. Likewise the part about engines evolving from military applications and their placement on the aircraft. Still, I find it funny that there hasn't been a more continuous drive toward higher bypass engines, given that better fuel efficiency and lower noise sounds like a win-win regardless of oil prices. Though I guess the same is true for cars, sadly.

@Flambino: Yes, it is a win-win, but the manufacturers first had to overcome the hurdle to start the development. This needed the pain of much higher oil prices. Once the engines were available, all new aircraft had to use them to stay competitive. That is why you have almost no motion and then a sudden jump.

Again: Makes a lot of sense. I just can't help but find it a strange economic artefact that engine manufacturers and/or aircraft manufacturers wouldn't make the occasional incremental change on their own. I believe the business term is "proactive". Sure, if customers demand better fuel efficiency due to oil prices then it'll happen, but I could also see companies one-upping each other more regularly instead of staying in lockstep like they have.

@Flambino: Read Dilbert, and it should all become clear. All the companies  involved are run by managers, not far-sighted visionaries.

It's that bad, huh? Yeah, I suppose it is. It's a fun contrast to other industries, where companies routinely descend into (often ridiculous) competitions for things customers haven't really asked for (e.g. 4K TVs when there's little-to-no content for them). Not exactly visionary stuff either, but sort of the opposite result.

There's also an element of the fact that if you just upgraded to a 5:1 engine, you're not likely to be in a rush to swap that out for a 6:1 engine a year later due to the cost/benefit not lining up. Swapping that 5 years later for a 9:1, however, is a different story as you're getting more benefit and are closer to the time you'd have to replace it anyway (ie less sunk cost)

@JonStory Oh certainly (though it's more like a 25 years between swaps). That was my own theory for this; the carriers sticking to certain models of plane and powerplant, thus dictating development (or lack thereof). Makes sense for the carriers. But there are a lot of carriers - at least since the 1980s - so even if carrier A will stick to its fleet of 5:1 engines for the next decade, carrier B might be in the market for shiny new planes. So you'd think there'd be a market for a 6:1 engine, and then a 7:1, and so on. Instead everyone just buys the same stuff for 25 years - or more.

@Flambino: with consumer goods like 4k televisions it's not necessarily important that anybody has asked for it. As long as it sounds cool and prestigious, some people will get convinced they want it just because it's available, even if it doesn't really make sense. Hence, offering such products means immediate financial gain for television manufacturers etc.. OTOH, if your customers are companies like airlines, every expenditure will be thoroughly checked on whether it really makes sense economically.

@leftaroundabout Oh, I know the 4K tv thing isn't a great comparison for a host of reasons. But I still find the contrast funny. For the consumer electronics it's very much "invention is the mother of necessity", and someone will always buy the latest stuff, whether or not it makes sense. And for the airline world it's exactly backwards - extremely so. It seems like everyone would like to build/buy new engines more often, but it's just a stand-off instead, with both sides settling for the same stuff for decades, until something else comes along to break the stalemate.

@Flambino: The proven stuff works. If you go a new route, you have to get the new gadget certified and accepted by a skeptical workforce. When safety counts, Oh…shiny! will not be enough.

That UDF is one mean looking engine.

The Comet's wing roots weren't actually a design issue for the Rolls-Royce Conway, as the Conway-powered Comet (the Comet 5) was to have had podded engines, instead of the buried engines of the Comet 1-4.

@Sean When Conway development started, the Comet 5 was still far out in the future. Rolls-Royce could not anticipate what DeHavilland would plan a decade later. Also, the Victor was as much a reason to keep the bypass ratio down, and no podded engine version of the Victor was ever started.


text:
How much does it cost the airline if an aircraft makes a missed approach?
aircraft go around due to variety of reasons viz. Bad weather (inevitable), unstable approach, ATC errors etc.
knowing the cost implications will help in educating the stakeholders.

Considering the potential cost of not executing a missed approach when warranted, surely the cost of going missed must be smaller. Which stakeholders are you looking to educate, and what education do you feel they need?

Sometimes the stakeholders are usurped by things beyond the stakeholders control.  I was on a shorter flight from somewhere in Texas to somewhere in Colorado, coming down final in the clouds, when the engines spun up and we went around before we broke out of the clouds. Turns out a truck had pulled up and blocked the ILS signal. I guess pilot notified tower, tower contacted someone else and they got the truck moved away.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What are the forces acting on the doors of the main landing gear?
When opening and closing the landing gear doors, what forces act upon them and how much power would the actuators need to exert upon the doors to open/close them mid-flight (assuming the landing gear cavity is not pressurised)? I haven't found anything on the actual doors in my research, only the landing gear itself, so I would appreciate some sources if you can provide them.

Your question is probably too broad. It depends on the opening direction and the geometry of the doors itself. For the aerodynamic forces modeling them as flat plates is probably good enough, I wouldn't be surprised however if ground handling forces are the critical ones.

I agree with Gypaets that this is going to be too broad for a definitive answer and will probably be closed as such if you can't boil it down to something more specific. There are many ways the doors can work. Some doors have separate actuators, some are mechanically attached to the gear extension mechanism. Some doors close or partially close after the gear is extended. It's going to be different for each aircraft type.

Aircraft have a maximum gear extension speed (V$_{LO}$, as in maximum landing gear operating speed), which is normally 1.6 times stall speed, so when the doors move, the dynamic pressure is rather low. Therefore, the forces during gear extension are not the only ones to check.
In cruise, suction on the gear doors might be the limiting factor for both stiffness and strength of the door itself, its latching mechanism or the hydraulic cylinder. I had the misfortune once to live through a flight test where part of one main door broke off in flight: It had no latch and was held shut by the hydraulic cylinder, which was mounted near the rear edge of the door. Suction and elasticity caused the forward edge to be pulled out into the airstream, so it soon became an air scoop, which only increased the pressure difference between the gear bay and the outside. Consequently, the door failed and needed to be redesigned, now with the actuation mechanism near the forward edge and an added latching mechanism.
If the door is aligned with the flight direction, make sure you look at the forces at maximum operating speed and maximum sideslip angle and treat the door like a regular fin. If the door opens into the airstream, use the proper drag coefficients for a flat plate and add some margin to account for oscillating flow separation. Make sure that the eigenfrequencies of the door or its operating mechanism are nowhere near the frequency of such flow patterns.
Here is a short note on the T-38 strut door loads which was written on occasion of the qualification of the T-38 as a chase plane for shuttle re-etries. The maximum gear extended speed had to be raised so the T-38 could follow the shuttle on the way down. Unfortunately, only measurements are given.

Why 1.7x stall?

@pericynthion: I thought Part 23.729 gives VLO as 1.7VS, but is is actually 1.6VS. Corrected.

Good answer.. maybe a quick note to add: "the actuator force depends significantly on the design of the mechanism." The door loads are more of a structural sizing property, of course also affecting the actuation design.


text:
Is the 737 Max's AOA disagreement warning light an actual light?
The New York Times article Boeing Believed a 737 Max Warning Light Was Standard. It Wasn’t. includes the following:

When Boeing began delivering its 737 Max to customers in 2017, the company believed that a key cockpit warning light was a standard feature in all of the new jets.
But months after the planes were flying, company engineers realized that the warning light worked only on planes whose customers had bought a different, optional indicator.

later:

The warning light notifies pilots of a disagreement in the sensors that measure which direction the plane is pointed, a potential sign of a malfunction. This light could have provided critical information to the pilots on two flights that crashed shortly after takeoff in recent months.

and later:

Because only 20 percent of customers had purchased the optional indicator, the warning light was not working on most of Boeing’s new jets. Neither Lion Air nor Ethiopian had the indicator.

note: All instances of boldface have been added for emphasis.
My question is asked to clarify the nature and appearance of the warning light itself.
Is this a physical light bulb-based indicator on a physical panel, or is it graphically implemented within a flat panel display screen? In either case, if the option described above was not purchased, is the (now non-functional) warning light still present and visible?
In that case, is there any secondary visual indication that would allow one to know that it's not working?

It is an ECAM message, but I can't find an image for you right now to post it as an answer. It is not a "bulb light".

@RonBeyer ECAM (Electronic Centralized Aircraft Monitor) is a term exclusively used by Airbus. The equivalent Boeing term is EICAS (Engine Indication and Crew Alert System).

In the B737MAX, being a full glass cockpit, the light 'AOA Disagree' is indicated by an alert on the PFD (rather than a physical bulb). This is why Boeing was selling it as an option: it is just a software change to show or hide 'AOA Disagree'.

Image taken from B737 MAX FCOM 10.10.33

Thanks for the clear and concise answer. To complete the answer; when there is no disagreement, I assume that there is no "AOA AGREE" indicator. One wouldn't be able to tell the difference between agreement and absence of the optional feature, correct?

That's correct. Further insight (anyone correct me if wrong): in the B737NG the light is not an option so pilots expected the light to be present in the B737MAX, too. Management who chooses aircraft may have thought to save money on this "option" (just one line of code for Boeing...) or Boeing wasn't clear. Result is aircraft with missing alerts.

Unfortunately, this repeats a misconception spread by mass media. The AOA Disagree indicator is not an optional feature. The issue was that there was a bug where the AOA Disagree indicator doesn't work unless the optional AOA gauge was selected. The bug was scheduled to be fixed in the next release. See this Boeing statement for an accurate description of the situation.

@Afe can you look into this, and then update (by reposting) your comment? I don't have any personal expertise here and it's hard for me to understand the nuances here. Thanks!

@user71659 Thank you for the link. What does Boeing mean for 'installing the AOA indicator'? What is the difference between 'AOA Indicator' and 'AOA Disagree alert'? The AOA vane is always installed (or not?)

@Afe The AOA indicator is a gauge on the PFD that indicates the readout relative to the stall limit.

@user71659 ahh I understand now!

Boeing claims in its statement that the AOA Disagree alert is not necessary "for the safe operation of the airplane" and that a change to start providing it on the standard MAX could wait since it was only to be included for "commonality" with earlier 737 models.


text:
What kind of drone might be able to fly so high that it "operate(s) outside national boundaries"?
In the question What is a propellant burner trailer? I mention that

CNN and NPR have pointed out that the US president recently tweeted a surveillance photo of an explosion of a rocket on a launch pad.

The NPR article linked above speculates on the source of the tweeted surveillance photo, mentioning that it might not be a satellite product. At one point it says:

It was not entirely clear where the president's photo came from. Panda believes it was most likely taken by a classified U.S. satellite. But Melissa Hanham, deputy director of the Open Nuclear Network at the One Earth Foundation, believes that the resolution is so high, it may be beyond the physical limits at which satellites can operate. "The atmosphere is thick enough that after somewhere around 11 to 9 centimeters, things get wonky," she says.
That could mean it was taken by a drone or spy plane, though such a vehicle would be violating Iranian airspace. Hanham also says that the European company Airbus has been experimenting with drones that fly so high, they are technically outside the atmosphere and thus operating outside national boundaries. But she says she doesn't know whether the U.S. has such a system.

This comment suggests that answers to Is there a height limit to national airspace? address the height required to operate outside national boundaries, so I have modified my question to ask only the following.
Question: What kind of drone, Airbus or otherwise, might be able to do this?

slightly related: What would a “Kármán plane” look like, a bird, or a plane?

Please try to avoid asking two questions in one. I think your first one is probably answered here.

@Pondlife edited, thanks for the link!

For what it's worth, the NPR article makes zero sense - if the atmosphere is limiting the maximum resolution, a drone flying at the edge of the atmosphere would be just as limited.

@Sanchises it's not so simple. The way that the atmosphere limits resolution for a given scenario depends on where the turbulent layer is between the observer and the object, and also how far the observer is in absolute distance. Usually half of the seeing effect comes from the boundary layer, while the other half from the troposphere/stratosphere boundary (7km to 17km).

@Sanchises Also see answers to Atmospheric influences on earth to satellite visibility and vice versa (e.g. atmospheric seeing)

@uhoh You make a valid point, although 60 000 ft is over 18km high (so you're still seeing the troposphere/stratosphere boundary) and if I understand it correctly, a drone would actually be more limited than a satellite according to your second link.

@Sanchises 66,000 feet is 20 km, the lowest apoapsis of a spy satellite is roughly 200 km, so everything is ten times larger seen from a drone roughly. Also, the aperture can be 10x smaller for the same diffraction limit (measured in cm at the ground) so the smaller drone telescope's aperture is closer in size to the cell size of the turbulence. I don't think you can draw any simple conclusions without doing a careful analysis.

Normally, controlled airspace ends at 60,000 ft (Flight Level 600). Airplanes flying higher than that would be operating outside of controlled airspace. Currently, there is no internationally agreed definition where national airspace ends. However, aircraft flying higher than 60,000 ft (18,288 m) could claim to fly outside of national boundaries.
There are several airplane designs capable of flying above that height:

The venerable Lockheed U-2 should be first on this list, even though it is sometimes loaded with sensors such that it can climb above FL600 only at the end of its mission.
Next would be the Lockheed SR-71, but none are still flying.
Both the Myasishchev M-17 and the larger M-55 also qualify.
But most likely the photo has been taken by a RQ-4 Global Hawk which officially flies up to 60.000 ft high.

Even though those designs fly at a height where 98% of the atmosphere is below them, they are still firmly flying within it, technically or otherwise.
There are several more which can fly much higher, but those are research aircraft which do not take photo trips into Iran. Of course, there can still be a classified design of which we don't know yet.
EDIT: Now it is reported that satellite tracking has identified the source of the photo as USA 224, a spy satellite launched in 2011. Using the shadows in the picture as a sun dial, the exact time could be determined and the corresponding satellite was traced down by amateur satellite hunters.

Thanks! I found this answer interesting as well.

@uhoh: You are very welcome!

The service ceiling of the PR9 variant of the English Electric Canberra was classified, but pilots' tales suggest it was well in excess of 60,000 ft, and a bomber Canberra broke the world altitude record in 1957 (70,310 ft)

just fyi there is still some thought that the now-famous tweeted photo was taken by a satellite; cf. Scott Manley's new video What a Tweet Tells Us About US Spy Satellites

@uhoh: Yes, that is a possibility, but I am no expert on the resolution of modern satellite cameras. The GH operates in the area, has the required cameras and is known to reach up to 73.00 ft.

@uhoh: Now it looks lie it was a satellite after all. Answer appended.

looks great, thanks!

FYI, above FL 600 is Class E airspace in the US, which is still controlled.

@JScarry: The question is about Iran, not the US. Please read the question for context!

@PeterKämpf You made a generalization about controlled airspace that is not correct. Class A varies by country and according to Wikipedia 'Class A is established from FL235 – FL460 throughout the whole Baghdad FIR.' in Iraq. In other countries it can be as low as FL 195. Your conjecture in the first paragraph is not correct because whether ATC exerts control over airspace has nothing to do with national boundaries.

@PeterKämpf The last sentence in your first paragraph should be revised. As far back as May 1960 both the Russians and Gary Powers knew that 70,000' was well within the national borders of Russia. And on October 27, 1962, U-2 pilot Rudolf Anderson Jr. was shot down during the Cuban Missile Crisis. In both cases,the US knew it was violating the airspace of other countries but thought it could get away with it.

@PeterKämpf nobody is trolling here, please avoid throwing accusations around. If you don't want to answer, nobody will force you. But if you decide to engage, please remain respectful of others.

Depending on who you ask, outer Space starts between 80 and 150 km, whereas 100 km is the most common defintion (Kármán line).
Countries do not acknowledge the transition from airspace to outer Space as territorial boundaries. Instead the function of an object is used for distinction:

if it flies, it must be an aircraft and subject to national sovereignty
if it falls around earth, it must be satellite and subject to Space laws

This distinction works well enough because there is hardly any traffic that could be both. Launchers and missiles are another class. As long as they go up or down, they will clearly be subject to national law at some point. When launchers or missiles are merely  crossing over a country, it will be a question of friend or foe.
To answer the question, no object can fly high enough to leave national boundaries, because the act of flying itself makes it part of the sovereign territory.
In order to operate above national boundaries, a drone would have to stop flying and convert to any sort of spacecraft, that is a satellite, a space probe, or a space plane. At the current state of technology, such conversion towards Space is impossible. Only launchers are capable of bringing objects into orbit. Re-entrance of a drone from Space on the other hand side is possible and has happened. See ESA IXV for instance.

Artist impression of IXV in Orbit. Image: ESA
This reentry vehicle has some maneuvering capabilities and no engines.  A vehicle like this satisfies the definition of a drone during the descent phase, and may be equipped with any sorts of instruments. If it reentered above a country, it would be very hard to agree on the altitude when it entered a national territory. In the end, the fact that it reenters the atmosphere, becomes an aircraft and subject to national territories is undeniable.

IXV flight path. Image: ESA


text:
What is the procedure for landing on an aircraft carrier?
What is the procedure for landing on an aircraft carrier? How is the checklist different from a regular landing?

Much more prayer!  Especially on night traps!  (There may be no atheists in a Foxhole, but I wonder if there are any in an F-18 or F-14 during a night trap...)

Landing on "The Boat"
Glossary

Approach turn/ 180: The approach turn itself is a 180 degree turn (190 degrees at the boat because of the angled deck) that is usually broken down into 5 segments: the 180 position, the 135, the 90 (halfway through the turn), the 45 and the groove.  Each respective position indicates the number of degrees left in the turn prior to rolling out in the groove.
(The) Ball or Meatball: an orange orb of light emitted from the IFLOLS.  A green horizontal row of lights (known as the datum) indicates proper glide slope.  If the ball is below the datum, the aircraft is low, and if its above the datum, the aircraft is high.  Aircraft should strive to keep the ball on the happy side.
Ball Call: Format: "(Side-number) (aircraft type) ball, (fuel-state), (auto-throttles)" Example: "123 Rhino ball, 9.0"
Carrier Break: A type of left hand overhead performed at 800ft AGL and 350+kts (for hornet guys)
BRC: the basic recovery course.  The course at which the ship is currently traveling, which does not include the offset for the angled deck.
Groove: the final portion of the approach (what civilians might call short-final)
Initial: on BRC, 3-5nm behind the ship, 800ft AGL, 350+kts, the starting point for the day approach
Interval: the specific aircraft in the pattern whose approach will commence just prior to yours, and whose separation you are responsible for not violating.
On speed: the proper AoA that will achieve the correct hook angle to catch the target wire of the carrier.  On speed airspeed can be approximated by the aircraft weight, but the term on speed does not refer to airspeed specifically, but units of AoA.
Side number: The 3 digit number assigned to the aircraft.  This is not the buno number (military aircraft don't have N numbers), it is a squadron specific identifier.  I will hence refer to '123' as the default side number.

Carrier Procedure
For simplicity's sake we'll pick it up at initial.  Glossary items have been italicized for ease of reading.

"123 flight of x, initial", ATC will then give the required instruction.
The flight will then side-step to the right of the carrier island, and begin looking for their interval.
Reaching the carrier, the flight will then perform the carrier break on their interval, ensuring that aircraft will arrive in 60 second intervals.
Landing checklist: 3 down and locked, flaps full, hook down, antiskid off, dispenser off, on speed XXX.
Once turned downwind, the aircraft will descend from 800ft AGL to 600ft AGL (the carrier pattern is flown at 600ft), and the aircraft will ensure it has proper lateral separation (abeam distance) from the carrier so as not to overshoot or undershoot on the approach turn.
Once abeam the LSO shack (or when the white of the round down is visible), the aircraft will increase VSI to approximately 200-300fpm and begin a 27-30 degree AoB turn.  Proper time in the groove is limited to only 15-18 seconds.  Too long or too short in the groove and the LSO can wave you off, so it is paramount that the approach turn be performed at the proper position.
At the 90, altitude should be 450ft AGL, and VSI should increase to 500fpm.
At the 45 the aircraft should be crossing the wake of the carrier, altitude should be 325-375ft AGL, and the ball should appear to rise. Note: Rolling into the groove, the ball should appear either centered or slightly high.
Once in the groove, with a visible ball, the aircraft makes its ball call.  The LSO will respond with "roger ball", which is the aircraft's clearance to land.
Once established in the groove, the aircraft should be roughly 700fpm and flying the ball for glidepath.  The pilot's scan becomes: meatball, lineup, AoA, meatball, lineup, AoA, meatball, lineup, AoA (you get the point).
As the aircraft flies in the groove the runway will constantly slip to the right requiring small, almost imperceptible, lateral stick inputs (and matching power corrections to account for the loss in lift).  The pilot will strive to keep the aircraft on centerline, on speed, with a centered ball.  Note: failure to keep the aircraft on speed can result in either a bolter, or an in-flight engagement.  It is imperative the aircraft maintain the proper AoA.
Just prior to touchdown, as the aircraft passes over the ramp, the pilot's scan will shift to ball, ball, ball, ball, ball, and the touchdown should come as a surprise.  This is referred to as "flying the ball all the way to touchdown".  Pilot's that deck spot (ie, attempt to fly to a specific spot on the deck) often fly down through the glideslope at the last moment and land short.
Once on the deck, the throttles will go to full military power (just shy of AB), and when landing has been assured, then the power will be reduced and the aircraft taxied off the landing area.

Shore Procedure
Naval aviation revolves around flying at the boat.  It is imperative that the procedures used at the boat become second nature, that they become ingrained in muscle memory.  To this effect, all shore based VFR approaches will be flown in exactly the same manner as would be at the carrier, with a few minor exceptions:

Antiskid will be on
The hook (for a non-emergency) will be up
Aircraft aren't required to have 60 seconds of separation, we routinely land with aircraft taxiing down the runway.
The throttles will be retarded unless executing a touch and go.

Otherwise, naval air stations that house carrier based aircraft all have I/FLOLS installed, and the ball is flown during normal VFR approaches to the field.

Further Reading
(Edit)
The following link, provided by the Chief of Naval Air Training Command (CNATRA), is an unclassified, publicly available, training guide used to train potential Naval Aviators to land on the boat for the first time.  The procedures are nearly identical, with a few nuances related to T-45 training operations, to the procedures used daily by fleet aviators.
Legal Notice.
Link to document provided by CNATRA.

"AGL" - is that relative to the ocean surface or the deck? I suppose if it matters at all it would be in the pattern.

@radarbob Good question, its always the ocean surface. We have radar altimeters we use to give us our precise AGL altitude.  Once you roll into the groove if you fly a good ball the deck height will take care of itself.

Are shore procedures even the same for people in planes that can't fly on carriers (e.g. P-3s)?

@cpast No, only carrier aircraft use carrier based procedures on shore.  As for helicopters, who knows.  They fly by magic anyway.

That's a great description.  I'm pitted out just reading it.

Don't think I'd ever come across this question before. Fantastic answer! Thanks for providing the detail!!

There are a few differences in landing on an aircraft carrier versus on the ground.
I've got no carrier (or military) experience so I can't really speak to the checklists, except to say that they would be slightly different for each aircraft, but it's a subject that's interesting to me so I've done a little digging over the years.
These are the differences that always stick out in my mind:

The whole airport is moving
When setting up for launch or recovery carriers typically "steam into the wind", creating a combined headwind of whatever the winds on the sea are, plus the speed of the carrier.  This minimizes the deck speed of landing aircraft, and is advantageous for takeoffs as well.
As an example, if you've got a 10 knot breeze and the carrier is steaming along at 30 knots into the wind the effective headwind on deck is 40 knots, so aircraft landing have a deck speed (ground speed) about 40 knots lower than their indicated airspeed, which makes decelerating them easier.
The arresting gear (Hook & Wires)
Even with the headwind above, modern carrier-based aircraft - with the exception of helicopters - touch down with some substantial forward velocity. They would not be able to stop using conventional thrust reversers and brakes, so in order to actually STOP the aircraft on the deck arresting gear is used to rapidly decelerate it.
The "full-throttle touchdown"
As Cameron pointed out, part of normal carrier landing procedure is to set the aircraft's engines to maximum thrust as soon as your wheels hit the deck, in preparation for a "bolter" if you miss the arresting gear (or it fails to stop your aircraft).
This is due to the short deck -- there is generally insufficient distance for either a rollout/stopping the aircraft with brakes or the pilot's reaction time for a "touch-and-go" when they realize they missed the wire. With the engines at full thrust the pilot is already accelerating and preparing to climb out and try again.
The approach slope guidance (Optical landing system)
This is the "ball" you hear pilots talking about in all those naval aviation movies, this is the equivalent of the various land-based approach slope systems (PAPIs/VASIs).  In the US Navy the optical landing system is controlled by the Landing Signal Officer (LSO), who also issues instructions to the pilot as necessary to facilitate safe recovery of the aircraft. My understanding is other navies with aircraft carriers have a similar person on deck.

Note that all of the above is for fixed-wing aircraft.
Helicopters can and do land on aircraft carriers too, but their procedures are much closer to "normal" (land) landings, because of the nature of helicopters.

The airport is moving up and down, as well as "steaming" into the wind.

@DanPichelman Indeed, this is part of why we needed LSOs and the OLS. It's hard to judge your approach when the runway is moving up and down.

A friend of mine told me you put in full thrust before your wheels even make contact, because it takes a while for turbines to spool up to full thrust.

What about the angle of attack? Is there any flare?

@Manfred That'd be a question best answered by someone who's done a carrier landing. From some videos there's definitely a touchdown attitude, but I don't see the same sort of roundout/flare like you'd do in a light GA plane. It looks closer to the textbook short field approach where you try to put the wheels on the numbers & make a "firm arrival" (followed by the arresting gear jerking you to a stop...)

@Manfred Years ago I checked out a carrier pilot in a Cessna 182. He found it very difficult to flare. He said that's a big no-no for carrier landings, and that they want a 4G touchdown impact.

found an old instruction video on youtube

@MishaP yes, though that's of course dependent on the aircraft. Some can spool up much faster than others

@voretaq7 The OLS used by the US Navy is the IFLOLS.  It is a self-adjusting lens that compensates for ship movement, and aircraft hook-to-eye distance.  Except for in the most extreme sea states (or for practice), the LSO does not manually control the movement of the ball.  The LSO's act as a sort of visual final controller, visually monitoring the glideslope and lineup of the aircraft, and warning the pilot of developing unsafe trends during the approach.

@SHAF Yeah, my understanding is they (or someone onboard) punches the aircraft type into the OLS, and everything else is compensated for by the system unless the LSO triggers a wave-off. I seem to recall reading somewhere that the first-generation systems were more manual (LSOs would move the ball), but I can't dig up that reference and I'm sure it's largely obsolete these days.

@voretaq7 Yep, the lens is adjusted for each aircraft type prior to that aircraft commencing the approach. The LSO's move the ball manually when the seas become to rough for the lens to compensate. This is usually a very sucky day for the pilot.  I'm not sure about older gen stuff though.

It's been a while since my last trap; 20 years or so. But, I spent a significant portion of my life flying on and off aircraft carriers. 597 traps (200 night) on 11 different carriers, from 1983 until 1995. I was also a Fleet LSO and a TRACOM (Training Command) LSO (Landing Signal Officer).
In my books I often write about carrier operations, so I have stayed in tune.
First: there are three types of approaches. Case I, Case II and Case III. Case III is for night and instrument conditions. Each aircraft or flight is assigned a holding altitude and fix (radial/DME) then penetrates on a TACAN approach, arc to the final bearing then picks up a raw data ILS.
The crew must push from their fix and alt with in +/- 10 seconds at 250 knots. You penetrate at 250 flying up the reference radial until 15 DME, turn to put the head of the needle on your wing and arc at 12 DME until you pick up final bearing FB (which is not same as Base Recovery Course, the BRC is heading of ship which is 8-13 degrees different depending on angle deck of the ship). The FB is aligned with the angle deck (actual landing area). Altitude is 1200'. At that point you pick up the CILS (like civilian ILS it gives you course and glide slope info on attitude indicator). At 10 miles (DME) from ship approx you put gear, flaps and hook down at 3 miles you intercept glide slope, pop out speed brakes and slow to on speed (optimum Angle Of Attack AOA) and start down. In the cockpit on the glare shield (dashboard), left side is a visual AOA indicator. It has two chevrons: \ / top (green), / \ bottom (red), with a yellow circle 0 in the middle. At 3/4's of a mile the LSO picks you up for control and you transition to a visual approach: fresnel lens/meatball (glide slope), line-up (course) angle of attack (speed). At night LSOs watch for the external approach lights (same colors as indexer) for speed, engine sound for power setting, and their eye for line up and glide slope. LSOs can see deviations before the pilots and calls for corrections over the radio for example: "power" (you are low), "right for line up" (because of the angle deck, landing area moves left to right as you approach), EASY with it" (you are going high), and the one no Naval Aviator wants to hear: "WAVE-OFF!" (you scared them, or the deck is fouled and you have to go around and try again). The LSOs also grade every pass on a 4 point scale. Each grade is posted on a board on the ready room wall for all to see. If your grades and/or boarding rate suck for too long (there is a definite learning curve) you go home.
If all goes well; you stay on speed (yellow donut) that keeps your speed correct and the hook at proper hieght/position, you land on center-line pointed down the angle deck, AND you are on the proper glide slope +/- 2 feet; you snag the three wire go to full power, click off the external lights and when you feel that welcome tug you unlock and fold the wings...then get outta the way because your Airwing pal is right behind you. If things don't go well: high- you bolter (miss the wires) and go around, low- you get waved off, snatch an early wire (bad grade) or hit the ramp and blow up. Off centerline- you'll get waved off (in the EA-6B Prowler 10' off CL put the wing tip into the noses of aircraft parked on foul line), even if you are on centerline if course isn't correct you can end up in the parked aircraft...highly frowned upon. BTW, at sea, at night, it's darker than 10 feet up a black cat's a$$.
CASE 1: Is the fun approach and is for good weather. Normally it is done EMCON, no radios. Each squadron has an assigned altitude over head the ship, you circle in a left hand pattern, normally in a flight of 2 or 4. When the flight lead sees an opening he drops to 800 feet abeam ship, outside of 5 miles, and then turns 180 degrees and runs up the ship's wake at 350 knots. At the bow the lead breaks by kissing off the flight with a hand signal and rolling into an 80 degree angle of bank turn, speed brakes out and pulling into a 4 g's in the turn. At 250 knots, gear, flaps and hook down. Approaching mid-ship drop to 600', check distance and begin to slow onspeed. Abeam the LSO platform (left side/aft on ship) start a 25-30 degree angle of bank left turn. At the 90 position of the race track pattern, be at 450', crossing the ship's wake 325-375' and be on-speed. In the groove wings level for 12-15 seconds, center-line between your legs, centered ball, and on speed until touch down. Fun city. Any deviation causes a down grade, the airwing competes for best squadron and Top Ten Aviators by grade average.
CASE-II is a combination of both when weather is above 1000 feet cieling with 5 miles of visibility, but there is a solid layer of overcast (SOCAL in June). You hold, penetrate, and fly up the TACAN FB like CASE II until below the over cast. then you enter for a carrier break like CASE I.
CASE I- S**t Hot-1 approach. Same as CASE I except you have to have more speed than altitude. 550 knots indicated at 500 feet works marvelously. You must break no later than the bow of the ship or it doesn't count. 90 degree, 5 g left turn, speed brakes out. After 180 degrees of turn slowing thru 250 indicated; gear, flaps, hook down. Ease turn to 60 degrees angle of bank. Pull toward the 90 as gear and flaps program out. You will slow rapidly and jets have significant spool up time, so put throttles in approximately 80% range. Over the wake ease roll to 30 degrees angle of bank. Rolling into groove on centerline the aircraft will squat onspeed as the engines spool up like majic. snatch the three wire, full power, then jerk the power off as you are drug to a halt by the arresting gear. This will bounce you out of the wires as you fold the wings so you don't "sh*t in the wires", causing the guy 30 seconds behind you to go around. REALLY fun city! A warning: John Wayne in the break often becomes Slim Pikens in the groove...its a gamble!
So what makes it hard? Deck moving +/_ 30 feet is "challenging", ship changing course is fun, especially CASE III. Ship blowing tubes (smoke out stack) causing you to go IFR in the groove. Single engine or other emergency approaches. Or various things you or your fellow Aviators screw up. Blue Water, (no divert), also ramps up the pressure.
So that's it, quick and dirty, with bad punctuation. I've got to go clean the gutters.

If you want to read more you can go to lelandshanle.com or amazon for Leland Shanle's books.

Navy carrier pilots routinely land the same ashore as aboard ship with the exception of the tail hook being stowed ashore (unless you have an emergency that requires an arrested landing at the field) and not going to full power upon touchdown (not prior) unless you are doing a touch and go landing (or FCLP-Field Carrier Landing Practice).
Most navy fields that have carrier based aircraft will have an OLS system at the field for continued practice during most approaches.
Attitude (Angle of Attack-AOA) is set near the start of the final approach as part of the landing checklist. This attitude has the tail hook at the lowest point and keeps the nose high.
Being on the back end of the 'power curve' with this high attitude, additionally keeps the aircraft speed over the ground slower and the power settings higher to maintain flying speed and prevent stall. Upon landing this thrust becomes excess thrust enabling the aircraft to more quickly accelerate and get safely airborne in the event of a bolter.
Additionally the higher thrust setting minimizes any spool up time because you are already near max thrust.

AoA is not part of the landing checklist, and, generally speaking, you should be on speed long before you roll into the groove (sh#t hot withstanding) or before you cross the FAF. Also, the proper AoA (on speed) keeps the hook at the optimum trapping height, which is far from the heighest AoA, or lowest hook height. Flying in full slow, with the hook further down, can result in ramp strikes and in-flight engagements.  And if you want to get really technical, there are plenty of reasons why you might use military power prior to touchdown.  For example, correcting a high in the middle.

As I read over the posts one thing comes to mind that is worth pointing out if we are discussing differences in checklists between landing on the field and landing on the ship. The difference appears in the checklist with regards to how the ABS (anti-skid) is handled in the 2 environments. On land the pilot ensures that ABS is selected and on the ship they make sure it is deselected. This is perhaps more important than you would think as is borne out by the fact it was mentioned in every fly-off brief I attended.
It is an important distinction for at least 2 reasons, one maybe obvious and the other not so obvious. First, ABS is not engaged while on the deck because if it fails during taxiing it can be catastrophic. A runaway aircraft on the deck can cause all sorts of problems. Taxi speeds on the deck are closely controlled and slow. There is no need for ABS there.
Second, when you do your work on the carrier you are there for months at a time, and most of your landings are to a wire. No brakes needed on landing except when the Plane Captain tells you to apply them after pull back. The first use of your brakes after landing is commanded by the Plane Captain, and almost immediately after landing! This is an important point because old habits explode easy.
Now the time has come for the squadron to pack up and head home. The planes do a fly-off and arrive at their home base field with the anti-skid turned off. Sure there is a checklist, and your mind is transitioning from landing on the ship to landing at the field. You would be surprised how often that switch is missed, and missed by experienced pilots as well.
Every fly-off brief I attended I heard this one item emphasized, and even then forgotten at the field on touchdown. The fly-off occurred as we approached the US. The planes that could fly were launched so they could arrive at the Naval Base where the squadron was attached. Once the ship docked they had to be off-loaded and transported.
You are excited to get one of the aircraft for the fly-off, sure it doesn't have a radio, but that doesn't down it. Your family and friends are waiting for you at home. You attend the brief and the next thing you know you are airborne heading home. It was an uneventful flight in and now you are downwind at the 90, double checking your landing checklist. You do an OK underline approach to the box and immediately hit the brakes. Ooops. The ABS is not on, and the tower tells you, if you didn't hear it yourself, that you just blew your tires.

Don't know about a checklist, but I know that when they get ready to land (as in, they are about to touch down on the carrier) they set the engines to max thrust, just incase they do not hit the cable to slow them down. I thought that this video about it was cool.


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How is mass flow rate computed?
I have been wondering how the mass flow rate is determined by the area of the engine air intake surface and the incoming speed of the air.
In still air, it is understandable that a stationary engine takes in air at the same rate as it is exhausting based on the preservation of the momentum of the air. Then, the mass flow rate through the engine intake surface can be easily calculated.
However, in still atmosphere with the same engine solely mounted to an aircraft cruising straight, level, and at constant speed $v$, it is not obvious to me how to determine the mass flow rate.
In particular, keeping the air intake surface area unity, can we determine the mass flow rate based on $v$ alone?

Yes, the mass flow rate is based on the intake area and air velocity. But if the engine is producing thrust, then the engine air velocity has to be higher than the freestream velocity.

@fooot, it has to be faster than the free stream in the nozzle, but not in the intake as evidenced by the fact that in supersonic flight the air still must reach the compressor face at subsonic speed.

@JanHudec good point, so not necessarily higher than freestream, but could definitely be different.

@fooot, actually according to Peter it is almost constant.

@JanHudec well the pressure ratio changes between 0.84 and 1.37 assuming it equals 1 at M0.5... so the velocity is changing maybe +/-10%?

That's from a forward speed of 0 to M0.85...

@fooot, the pressure ratio is calculated from the assumption that the stream speed is constant M0.5 at the face of the compressor. The expression gives how the pressure changes when the air is accelerated/decelerated to that M0.5.

@JanHudec well of course if you assume it to be constant, then it is constant... and if it is constant at M0.5, there is a very good chance it's different from freestream, which is what I was trying to say.

The short answer is: No. One cannot calculate the inlet mass-flow based on the velocity alone. However in order to "know" the velocity ( $v$ ) you most likely would have measured everything you need (see below).
Your confusion with regards to the in- and outlet mass-flow might be based on the fact that the intake does not "collect" all air upstream depending of the flight-velocity.
The key is not to think of the geometric area of the intake but the area of stream tube around the air entering the intake.
The velocity upstream of the intake is not equal to the air-speed (subsonic flight) because the potential field of the intake decelerates (or accelerates) the flow upstream of the intake and expands (or contracts) the stream tube (from Wikipedia):

In order to calculate the mass-flow we need to determine the speed and the properties of the air.(please observe that the air-speed ( $u$ ) at the intake is not equal the free-stream-spped ( $v$ ) )
Usually the measured properties are:

Total Pressure, $p_\mathrm{t}$ (Pitot Tube)
Static Pressure, $p_\mathrm{s}$ (Static Pressure Port)
Total Temperauter, $T_\mathrm{t}$ (info, examples)
Relative Humidity, $\varphi$ (for simplicity not used below. Humidity changes the heat capacity)

The following equations are used to calculate the mass-flow ( $\dot{m}$ ). Simplifications are commonly made for slow speeds unnecessarily excepting a 5% error. The following approach does not use these simplifications.
The equation which needs to be solved in the end is:
$\dot{m} = A \cdot \rho \cdot u$
Neglecting blockage effects and non-uniformities, the density ( $\rho$ ) and the velocity at the inlet ( $u$ ) are unknown and need to be derived from the measured values.
First the Mach-Number is calculated by solving the following equation (see Nasa) for the Mach-Number, $M$:
$\frac{p_\mathrm{s}}{p_\mathrm{t}} = \left( 1 + \frac{\gamma - 1}{2} M^2\right)^{\frac{\gamma}{\gamma-1}}$
Here $\gamma$ is the isentropic coefficient which is around $1.4$ for air depending on the humidity.
Second, with the Mach-Number, $M$, we can use another isentropic relation to calculate the static temperature, $T_\mathrm{s}$:
$\frac{T_\mathrm{s}}{T_\mathrm{t}} = \left( 1 + \frac{\gamma - 1}{2} M^2\right)^{-1}$
Third, using the ideal gas law the density ( $\rho$ ) can be calculated:
$\rho = \frac{p_\mathrm{s}}{RT_\mathrm{s}}$
Here $R$ is the Specific Gas Constant.
Forth, using the equation for speed of sound, $a$
$a = \sqrt{\gamma R T_\mathrm{s}}$
Finally Fifth, utilising the definition of the Mach-Number, $M$, the air-speed ( $u$ ) can be calculated:
$M = \frac{u}{a}$
Now all missing values are available to compute the mass-flow.
This approach can easily expanded to cover humid air by adjusting $R$ and $\gamma$ with respect to the relative humidity.
As mentioned in other answers: The inlfuence of non-uniformity of the flow caused by boundary layers or inlet distortions (e.g. inlet-ducting) need to be corrected using a calibration.

You need pressure sensors, temperature sensors and flow speed sensors. All three together allow you to calculate the mass flow. Initially, this is done with arrays of sensors to find out about intake distortion and flow inhomogeneity. Once the intake has been calibrated, one discreet sensor of each type will do.


text:
Can a private pilot obtain a recreational pilot certificate?
While I'm thankful that third class medical reform has passed, I currently have a special issuance medical that the FAA has been reviewing for several months. This go around, they requested additional documentation further delaying the process.
I'm currently a private pilot. However, the aircraft I fly meets the requirements to be able to be flown by a recreational pilot. Looking at FAR 61.96, it doesn't look like I can "downgrade" my certificate with an additional recreational pilot rating per:

§ 61.96 Applicability and eligibility requirements: General.
(b) To be eligible for a recreational pilot certificate, a person who applies >for that certificate must:
(1) Be at least 17 years of age;
(2) Be able to read, speak, write, and understand the English language. If the applicant is unable to meet one of these requirements due to medical reasons, then the Administrator may place such operating limitations on that applicant's pilot certificate as are necessary for the safe operation of the aircraft;
(3) Receive a logbook endorsement from an authorized instructor who -
(i) Conducted the training or reviewed the applicant's home study on the aeronautical knowledge areas listed in § 61.97(b) of this part that apply to the aircraft category and class rating sought; and
(ii) Certified that the applicant is prepared for the required knowledge test.
(4) Pass the required knowledge test on the aeronautical knowledge areas listed in § 61.97(b) of this part;
(5) Receive flight training and a logbook endorsement from an authorized instructor who -
(i) Conducted the training on the areas of operation listed in § 61.98(b) of this part that apply to the aircraft category and class rating sought; and
(ii) Certified that the applicant is prepared for the required practical test.
(6) Meet the aeronautical experience requirements of § 61.99 of this part that apply to the aircraft category and class rating sought before applying for the practical test;
(7) Pass the practical test on the areas of operation listed in § 61.98(b) that apply to the aircraft category and class rating;
(8) Comply with the sections of this part that apply to the aircraft category and class rating; and
(9) Hold either a student pilot certificate or sport pilot certificate.

Specifically (9). Is there a way I can exercise the privileges of a recreational pilot? I'm willing to take another knowledge test / checkride.

The type of flight, not the level of pilot certificate, set the medical requirements.  For example, an airline captain with an ATP does not need a 1st class medical to fly his personal C-152 just because ATPs need 1st class medicals to do their job.

A third-class medical is still required for a recreational pilot (see 61.23(a)(iii)(2)). You may be thinking of a sport pilot, where you can fly with a driver's license instead? But that's only possible if you've never had a medical revoked or an SI withdrawn. It isn't completely clear from what you've said if that applies to you or not.

(The answer I posted this on looks like it was removed) There is another option to avoid losing your "currency", you could always go flying with an instructor. You don't need a valid medical (or even license) to fly with an instructor while waiting for your medical to get reviewed. Even with third class medical reform you may not qualify to fly if you've ever been revoked as @Pondlife said.

There are about 80 active recreational pilots. It's never been popular and continues to decline. The "downgrade" is generally basicmed.

In the context of your question, not technically.  You can hold different grades of certificates in different categories and classes, but there is no mechanism to "downgrade" an existing category/class-rating certificate.  Of course you could be a rotorcraft ATP holder, and then take a check ride to become a recreational-grade ASEL pilot, but that's not what you're really asking here.
What could do: You could opt to surrender your private pilot certificate to the FAA thus making you not a pilot, and then you could take a check ride for recreational.
Of course, there is no reason to do this at all!  You can do the same things as long as you're exercising the privileges of the lower certificate, then whatever medical rules are there should only apply for that operation if I'm not mistaken, but if there is a valid medical deficiency it really doesn't matter either because there are rules about fitness for flight.
Ie. I'm a private pilot and I get cancer and the FAA yanks my medical, I cannot just decide I'll go fly gliders now because they don't require a medical certificate.  The standard of fitness for flight always applies.

this is correct -- but I want to emphasize that regardless of the certificate you hold you may elect to exercise the privileges of a lower certificate.

Recreational Pilot is NOT the same as Light Sport. I think there have only ever been a couple hundred people with Recreational Pilot certificates. This predates LSA. Recreational Pilots can fly something like a 172, though with lots of limitations.
If you are thinking of a Light Sport Airplane, then, as mentioned above, your Private Pilot ASEL certificate includes all the privileges of the lower Sport Pilot certificate. Get checked out in the airplane and have fun.

Welcome to aviation.SE! I may have missed something  but I don't see any confusion between recreational and sport in the question. In any case, if you're new to StackExchange the [tour] meet be useful.

I suppose you could surrender your PPL to the FSDO, thence receive and log ground and flight training with an instructor for a recreational pilot certificate and pass both the knowledge and practical exams for RPL.
But why would you want to?
Recreational pilot certificates hamstring what you currently can do with your PPL ie no night flying, cross country flying, etc. without additional training and logbook endorsements, etc.  you would also need a current medical certificate to take the checkride as well.  In addition a RPL requires either a current medical certificate or BasicMed compliance in order to act as PIC aboard an airplane.
I’d say a better option for you would be to go the BasicMed route per Part 68 and just limit your PIC activity to the restrictions listed in Part 68.  It’s would be much simpler to do and offer you much more flexibility in your future flying.


text:
What are the "high performance characteristics" of a Boeing 777?
News of the potential further stretch of the A350-1000 have seen pretty much all journalists discuss the "high performance characteristics" of the competing Boeing 777-9 with Middle Eastern airlines. For example:

[...] the new Airbus jet would target airlines that need high-capacity, long-range aircraft but not necessarily require the same high-performance characteristics that have made the 777-9 so popular with Middle Eastern airlines. (The Gulf region can be hard on an airliner.)

What exactly are these? Why is the 777-9 suited to them and the A350 not?

The gulf region is very hot, something that can reduce aircraft performance. The 777-9 is better able to cope with that (due to the higher thrust from the engines and larger wing area).

I agree in principle with the take-off performance consideration. I would propose to refine the second part of the answer ( higher thrust from the engines and larger wing area) -> higher $T/W$ (maybe(probably), we don't know Airbus values yet). Another aspect that influences take-off performance is $L \over D$ of the flapped configuration and $Cl_{max}$

Do you have a source for the "higher thrust" and "larger wing area" for the 777-9? The 777-9 is a bigger plane overall than the A350-1000 (according to Wikipedia, its MTOW is 14% higher, and has 9% more thrust).